Water and wastewater treatment systems use a series of filters to remove debris of various sizes from untreated wastewater entering the system. Conventionally, water and wastewater influent have been pretreated using a screen such as, for example, a mechanical bar screen or rake, to collect and remove large object debris from the influent. Other mesh-type filters have also been used to remove smaller debris from the influent during pretreatment. However, these filters fail to capture particulate matter that is about 0.1 to 6 millimeters in diameter. Small undissolved suspended and floating particulate matter such as this may also bypass the seals, if any, used in conventional pretreatment facilities.
With each filter, one or more seals may be used to retain debris within the system so that solid objects do not bypass the filter. The seals may assist in capturing large object debris and flotsam from bypassing the pretreatment filters and entering into latter stage components of the water or wastewater treatment system where other equipment could be damaged. Solids in the water and wastewater escaping the system can damage or otherwise hinder the performance and increase corrosion of the downstream equipment of the system resulting in expensive repairs, the need to maintain a stockpile of replacement parts, decreasing the life and operability of the system, and causing down-time in the form of system maintenance outages.
Rotatable pretreatment screen assemblies have been developed to more effectively remove small suspended and floating particulate debris of about 0.1 to 6 millimeters in diameter from wastewater influent. This small particulate debris such as hair, seeds, small leaves and pine needles, plastics, and textile threads can clog and damage filters and other equipment used at the primary treatment stage. Such debris is also more difficult for primary treatment systems to remove because of their focus on sedimentation rather than on the removal of flotsam. The rotatable pretreatment screens used in the removal of small particulate matter can include multiple conjoined filter screens or other parts. A need exists for a seal that can effectively close any gap between the rotating filter screen assembly and its housing.